Re: [boost] Boost.Hana - Type Classes, data types and categories (tags).

Subject: Re: [boost] Boost.Hana - Type Classes, data types and categories (tags).
From: Louis Dionne (ldionne.2_at_[hidden])
Date: 2014-09-20 11:03:42

Niall Douglas <s_sourceforge <at> nedprod.com> writes:

> 
> On 17 Sep 2014 at 20:49, Louis Dionne wrote:
> 
> > I had not thought about the issue because right now, name clashing is
> > avoided simply by not having two functions with the same name. This has
> > worked well so far. Since this is the simplest way to do things, I'd
> > rather keep it that way. Of course, if I need to introduce a function
> > whose name would clash, then I will strongly consider your suggestion;
> > thank you for that. 
> 
> namespaces can be used for disambiguation, but they are actually much 
> more useful and powerful than that. You can map namespaces into other 
> namespaces, mash up namespaces into customised variants and with 
> template aliasing you can now easily metaprogram namespacing too, so 
> you could have the results of a Hana operation cause one set of 
> things to be mapped into some destination namespace as against 
> another set of things. And then, you see, a bind() function can 
> actually have metaprogrammed meaning and implementation which is not 
> only neato, but very intuitive for the end user.

I'm not sure I understand you. I do understand how we can map namespaces into 
other namespaces:
    
    namespace A { }
    namespace B = A;

I also understand how we can mash up namespaces:
    
    namespace A { }
    namespace B { }
    namespace mash {
        using namespace A;
        using namespace B;
    }

But I don't understand how template aliases come into play and give me more
flexibility. Would you care to give a basic example of what you meant?

Thanks,
Louis